Chain saw bar

ABSTRACT

A chain saw bar having a sprocket rotatably mounted in the nose of the saw bar guiding a saw chain around the outer end of the saw bar. The sprocket is rotated on roller bearings that are supported by an inner race member that is fastened between two sideplates that form the nose of the saw bar. The means for fastening the inner race to the sideplates includes a removable lock mechanism having a pair of stud members. A stud member is inserted through each side plate to independently lock the inner race to each sideplate. With the aid of a simple tool a worn or broken sprocket can be easily removed from the saw bar and replaced with a new sprocket.

United States Patent [72] Inventor Norman C. Locati Lake Oswego, Oreg.[21] Appl. No. 875,700 [22] Filed Nov. 12, 1969 [45] Patented June 29,1971 [73] Assignee Omark Industries, Inc.

Portland, Oreg.

[54] CHAIN SAW BAR 5 Claims, 5 Drawing Figs.

[52] 11.8. C1 143/32 [51] B27b 17/04 [50] Field ,of Search 143/32, 32 H[56] References Cited UNITED STATES PATENTS 3,334,670 8/1967 Merz 143/321-] Primary Examiner-Donald R Schran Attorney-Robert L. HarringtonABSTRACT: A chain saw bar having a sprocket rotatably mounted in thenose of the saw bar guiding a saw chain around the outer end of the sawbar. The sprocket is rotated on roller bearings that are supported by aninner race member that is fastened between two sideplates that form thenose of the saw bar. The means for fastening the inner race to thesideplates includes a removable lock mechanism having a pair of studmembers. A stud member is inserted through each side plate toindependently lock the inner race to each sideplate. With the aid of asimple tool a worn or broken sprocket can be easily removed from the sawbar and replaced with a new sprocket.

CHAIN SAW BAR I This invention relates to chain saws used for harvestingtimber and more particularly to the chain saw bar on which the saw chainis supported.

It is a well-known problem in the industry that the outer end of theelongated saw bar, referred to as the nose of the saw bar, is subjectedto extreme wearing. It has become recently common to provide saw barswith sprockets rotatably mounted on the nose to eliminate the slidingfriction of the chain on that portion of the bar. Nevertheless thesprockets still wear out much faster than the remainder of the saw bar.and considerable savings in operating expense is realized by merelyreplacing the sprockets rather than the entire saw bar.

The saw chain is driven around the saw bar very rapidly and considerableand varying stresses are applied to the chain as it cuts through a log.I-Ieretofore, in order to withstand these varying stresses and stillhold the required chain guiding characteristics, the inner race on whichthe sprocket rotates was riveted to the bar. Where the sprockets arechanged in the field by the chain saw operators, the rivets are mostgenerally removed with a punch and hammer. This crude method of changingsprockets often causes damage to the bar and chain, is slow and tedious,and to satisfy even a minimum of success requires both know how andskill.

It is thus an object of the present invention to provide an improvedmeans for locking the sprocket to the saw bar which satisfies thementioned requirements and yet is easily unlocked to pennit quickchanging of the sprocket by the chain saw operator while he is in thefield. Very generally the preferred locking means of the presentinvention is used to fix the inner race of the sprocket between twosideplates that form the nose of the saw bar. The locking means for theinner race includes a circular central opening in the inner race withweb segments of reduced thickness closing off opposite side portions ofthe otherwise circular opening. A pair of studs appropriately shaped topass through the opening have grooves which are turned to engage the websegments. The unique characteristics and advantages of the lockingmechanism of the present invention will be more apparent when referringto the following detailed description and drawings wherein:

FIG. I is a perspective view of a chain saw such as would employ a sawbar of the present invention;

FIG. 2 is a sectioned view of the nose portion of the saw bar as takenon line 2-2 of FIG. 1;

FIG. 3 is a sectioned view as taken on line 3-3 of FIG. 2 butillustrating the sprocket unlocked from the saw bar;

FIG. 4 is a view similar to FIG. 3 but showing the sprocket locked tothe saw bar; and

FIG. 5 is an exploded view illustrating the various parts of the lockingmechanism.

Referring to FIG. 1 of the drawings, a chain saw is shown having a sawbar l2 supporting a typical saw chain 14. As will be apparent from FIG.2, the saw bar 12 has agroove 18 provided along both the top and bottomedges forming a channel in which the drive tangs 19 of the center linksof the saw chain are guided. The saw chain is supported on the saw barby the sidelinks 21 riding on the side rails of the groove 18. Thegroove 18 is substantially deeper at the nose portion of the bar formingtwo spaced apart sideplates 23. The spacing and deepened groove aresufficient as shown in FIG. 2 to permit the insertion of a sprocket 16between the sideplates.

Referring to FIGS. 2 thru 5, an inner race is adapted to be fastenedbetween the sideplates 23 as will be explained later. The sprocketl6'has a circular central opening adapted to fit around the inner racewith roller bearings 22 therebetween to permit free rotative movement ofthe sprocket around the fixed inner race. The inner race is positionedso that the sprocket teeth are inserted between the side links of thechain and so to engage the adjacent center links for lifting the chainfrom the bar as the chain passes around the nose.

Referring now to the means for fastening the inner race 20 between thesideplates 23, it will be seen most clearly from the exploded view ofFIG. 5 that the inner race 20 has a circular central opening 25. A pairof web segments 24 of reduced thickness are oppositely located on theside of the opening 25. A pair of identical lug members 26 are providedwith a flat head portion .27 and a shank portion 30. It will be notedfrom the dotted lines in FIG. 5 that each shank portion 30 is adapted tofit in one half of the circular opening 25 with a relief section 32 forbypassing the web segments 24. A groove 34 is provided in the shankportion 30 with a width and depth compatible with the width and depth ofthe web segment 24. When the shank portions 30 are properly insertedfrom each side into the opening 25 of the inner race, the grooves 34 arealigned with the web segments 24 and by turning the lugs the grooveswill be turned onto the web segments to effectively lock the lugs ontothe inner race.

The procedure for assembling comprises the steps of inserting the innerrace with sprocket mounted thereon between the sideplates 23 of the sawbar so that the opening 25 is aligned with openings 31 in thesideplates. A spring washer 28 is placed on the outside of thesideplates over the openings 31 and the shank of the stud 26 is insertedthrough the spring washer, and the aligned openings 31 and 25 in thesideplate and inner race respectively. It will'be seen from FIG. 3 thatthe head of the stud 26 engages the spring washer 28 before the grooves34 of the shank are properly aligned with the web segments 24. The studsmust then be forced against the spring bias of the spring washer untilthe head of the stud is bottomed against the sideplate as shown in FIG.4. The various components are designed so that the proper alignment ismade when this limiting position is achieved. The operator then merelyturns the lugs a quarter turn, ie. as with a simple screwdriver-typetool engaging a notch on the head of the stud.

It will be noted from FIGS. 3 and 4 that the sideplates 23 have recesses37 so that when the lugs are locked in place they are essentially flushwith the outer surface of the sideplates. This is important to preventthe lugs from rubbing as the chain saw bar is moved through the kerf ofa tree during the cutting operation. 1

Another feature is the means for holding the inner race stationarybetween the sideplates 23. Bosses 41 are formed on the inner wall of thesideplates which engage small holes 43 provided in the inner race. Thesprocket and inner race can however be easily removed after the lugs areunlocked by slightly spreading the sideplates to disengage the bossesfrom the holes 43. Grooves 45 are formed in the shank portions of thelugs to enable oil to be inserted into the roller bearings 22.

From the above it will be understood that a sprocket can be easilyremoved from the saw bar by turning either lug (which necessarily forcesturning of the other lug) until the grooves 34 are disengaged from theweb segments 24. The spring washer will then force the lugs partiallyout of the opening at which point they are easily removed (see FIG. 3).The sideplates are spread and the sprocket assembly is removed. A newassembly is inserted between the sideplates 25. The lugs are reinsertedthrough the washer springs and sideplates into the opening of the innerrace. By compressing the washer spring the grooves are aligned with theweb segments. The lugs are then turned 90 relative to the inner race(which is held stationary by the bosses 41 engaging openings 43) toeffect locking.

It is believed that the washer spring produces a constant pressure thatcompensates for the vibration and other forces to prevent the lugs fromunlocking. Also the pressure against the sideplates helps to retain theproper spread to avoid undesired lateral play as the chain passes aroundthe nose. Also it will be noted that the spring is substantiallycoextensive with the inner race so as not to pinch the sideplatesagainst the rotating sprocket.

Numerous variations and modifications of the invention will be apparentto those skilled in the art. Therefore it is to be understood that theabove description is intended to merely illustrate the invention and notto limit its scope which is determined by the claims appended hereto.

What I claim is:

l. A chain saw bar for supporting and guiding a saw chain in atree-cutting operation comprising a nose portion of spacedapartsideplates, an inner race and a sprocket rotatably mounted on said innerrace, said inner race and sprocket slidably received between thesideplates and releasable locking means for releasably locking eachsideplate to the inner race, said locking means comprises a pair of studmembers each with a head portion and a shank portion each sideplatehaving openings through which the shank portion is insertable, saidinner race and the shank portion of each stud member interlocked withthe head portion locking the sideplate to the inner race.

2. A chain saw bar as defined in claim 1 wherein the inner race has acircular central opening, a pair of web segments of reduced thicknessare located on opposite sides of the opening to partially restrict theopening, the sideplate openings are aligned with the inner race opening,the shank portions of the stud members being inserted through thesideplate openings and into the restricted opening of the inner race,said shank portions having grooves of a width and depth compatible withthe web segments, said grooves being in alignment with the web segmentswhen the head portion of the stud member is abutted against thesideplate, and means for turning the stud members relative to the innerrace to thereby slide the web segments into the grooves of the shankportions.

3. A chain saw bar as defined in claim 2 wherein a spring washer ispositioned around the shank portion between the head portion of the studmember and the sideplate for inducing constant outward pressure toinhibit accidental unlocking.

4. A chain saw bar as defined in claim 3 wherein the spring washer hasan outside diameter less than the inside diameter of the sprocket.

5. A chain saw bar as defined in claim 4 wherein gripping means betweenthe inner race and the inner walls of a sideplate inhibits rotativesliding of the inner race relative to the sideplate.

1. A chain saw bar for supporting and guiding a saw chain in atree-cutting operation comprising a nose portion of spaced-apartsideplates, an inner race and a sprocket rotatably mounted on said innerrace, said inner race and sprocket slidably received between thesideplates and releasable locking means for releasably locking eachsideplate to the inner race, said locking means comprises a pair of studmembers each with a head portion and a shank portion each sideplatehaving openings through which the shank portion is insertable, saidinner race and the shank portion of each stud member interlocked withthe head portion locking the sideplate to the inner race.
 2. A chain sawbar as defined in claim 1 wherein the inner race has a circular centralopening, a pair of web segments of reduced thickness are located onopposite sides of the opening to partially restrict the opening, thesideplate openings are aligned with the inner race opening, the shankportions of the stud members being inserted through the sideplateopenings and into the restricted opening of the inner race, said shankportions having grooves of a width and depth compatible with the websegments, said grooves being in alignment with the web segments when thehead portion of the stud member is abutted against the sideplate, andmeans for turning the stud members relative to the inner race to therebyslide the web segments into the grooves of the shank portions.
 3. Achain saw bar as defined in claim 2 wherein a spring washer ispositioned around the shank portion between the head portion of the studmember and the sideplate for inducing constant outward pressure toinhibit accidental unlocking.
 4. A chain saw bar as defined in claim 3wherein the spring washer has an outside diameter less than the insidediameter of the sprocket.
 5. A chain saw bar as defined in claim 4wherein gripping means between the inner race and the inner walls of asideplate inhibits rotative sliding of the inner race relative to thesideplate.